Technical The forbidden mid 50’s mopar poly’s

Hey i’ve been on here a bit but im still learning. One thing that ive had trouble finding any information on is the mid 50’s mopar poly engines. Ive heard a lot of good info on all the hemi’s however its “little brother” the poly is often overlooked in favor of the hemi. Im currently looking at buying a 56 Coronet Royal 2dr and it has the poly in it. Id like any info that the more experienced community might have for me. And dont worry, i do have a hemi im building, but ill have to decide between my current 50 Coronet 4dr or this coupe. Thank you


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That '56 is pretty bitchin'

 

I thought the only thing to do with those poly engines was to put Hemi heads on them

 

The Allpar site has a section about them. Hopefully someone with personal knowledge and experience will come along soon.

 

Well funny thing is im building a 55 despto fireflite hemi but im also interested in what other engines came in these things (other than the 230 flathead- thinking about it makes me shutter; bad experiences) but hey id like to see what the little poly’s can do and what they have a chance of standing up against.


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Or you could use only one Hemi Head.

 

I have some Hemi's under the bench, but am looking for a Poly, which I would use in a rod, particularly if open engine compartment. They are handsome, unique engines; Hemi's are everywhere (no disrespect intended).

 

Here is a site that has an encyclopedia of Chrysler information.
https://www.allpar.com/mopar.html#8

Link to the poly head
https://www.allpar.com/mopar/poly.html

My godfather had one in a 55 Dodge, and put an incredible number of trouble free miles on the car. My personal impression is that they were a great engine, but I never saw them in any form other than stock.

Bob

 

Sure, every where you look at a car show, but none under my bench...now if you're tired of looking at them and you have one....

 

@Hemihead_NHRA

Over the years I have read several articles that have stated that the poly head is right in there with the hemi and, if not, so close it doesn’t matter in most applications (excepting, perhaps, serious racing applications). But like 90 fin Buick brake drums vs the 45 fin version, they play second fiddle solely on the basis of esthetics, not function.

I have five Hemis, Dodge and Chrysler, and one Dodge 325 Poly for which I have a set of Hemi heads. However, I find myself indecisive about actually making the head switch, given the information I wrote above.

I love your avatar.......High n Mighty! an icon of MOPAR history!

Ray

 

Chrysler - it is said - learned soon after if came out in 1951 that is cost some money to produce a hemi and it was a big motor at that ! The shift towards smaller cars could be a factor as well. Any way - with the same block they started putting in non hemi pistons and started the Poly head revolution that lasted until about 1959. The trucks would carry the early hemi motors a year or so but the cars were done. Some Industrial hemis were sparingly produce for a few years. Some one can correct me but I think the first use of a poly head on Hemi block was in the Dodge line in 1954 with trucks getting the poly headed little Red Ram 241 inch motor. Dodge capitalized the use that "Red Ram" name on Polys and called the next hemis "Super Red Ram"....the came the D-500's in 1956 and 1957 325 motor. Chrysler was doing the same thru 1957 using the 1956 354 block with poly heads on the low price cars.
Plymouth used the Dodge motor in 1955 with Poly head's and when the got the new 277 V/8 in 1956 - it would become the 318 poly a year later in 1957. Please correct me as I don't know it all........

 

Great engines. Just expensive to produce, so the 'A' engine (poly), became the 'LA' in later years. Rotating assembly had very little changes. Cam changed due to the valve arrangement. Changes for cost reduction, not necessarily performance improvement. Remember when GM introduced the big block, dubbed 'porcupine heads'? Canted valves, tipped in the flow direction for good breathing. Take a look at a poly with the valve covers off.

yep, Mopar was there years earlier. Similar to GM's divisions, Mopar had too many variations. Dodge, Plymouth, Chrysler had very similar designs, but didn't share many parts or tooling.

Too bad they didn't continue performance development past the 50s, as the dual quad 318s where good performers stock.

 

What size would you like - 155, 241, 270, 341, or 354 cid? Unfortunately, freight cost would be prohibitive.

 

Trivia -- something I just learned a few days ago: the Dodge D500 was a 325 cid engine. However, a rarer model was called a D501, which was 354 cid (presumably, the Chrysler engine).

Question -- my observation is that the early Poly valve covers had a very pronounced scalloped side (see Hemi-Hemi picture above, posted by Hombre). Later ones seemed less pronounced, and more "saw toothed" than scalloped. Is it that the early style was just on the Hemi based engine, and the later style was just on the 277/318 based motors? Or did the 277 continue with the early style, and the change made with the 318?

 

‘56 D500 was a 315 hemi........’57 D500 was a 325. ‘57 D501 was an extremely limited volume factory drag package...and yes it used the ‘56 Chrysler 354 engine with ‘57 Chrysler driveline, suspension and brakes. The only one I ever saw in person was an ex-Arnie (The Farmer) Beswick’s 2 door post drag racer. That was just before he switched to Pontiac.

The 277 and 301 poly had the saw tooth valve covers and evolved into the 318. They are quite a bit different than the 241, 259, 270, 315, 325 which all had the tin valley cover and raised intake manifold, same as hemis. Whereas the 277, 301, 318 had different block and heads and the intake manifold was also the valley cover.

Ray

 

Dodge used a ploy 318 up through the 1966 model year. I had a 66 version in a 66 Coronet wagon. That was a very strong, tough motor Was still running with all its original parts (except the carb and tune up stuff) past 150,000 miles on the street. I also had 3 other 64-66 poly 318 over the years, (the 64 was in a motor home and said it was 205 HP on the 2bbl carbed air cleaner housing) all were good motors. The valve covers on all my poly motors looked just like the covers pictured earlier.
The 64 was the oldest poly I had. Gene

 

Thatnka for the info Ray! Theres a lot of good stuff that people are bringing up; one thing i do wonder is if anyone has speed parts for these small poly motors, or would some dodge hemi parts would work on it, like intakes or headers etc...


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@Hemihead_NHRA .....everything that fits a like model Hemi fits the Poly except the exhaust manifolds/headers, pistons and camshafts. Intakes, water pumps, ignition, internal parts such as bearings, lifters, etc. are the same for like model (meaning low deck Dodge Hemi fits low deck Dodge Poly. Low deck = 241,259, 270; High deck = 315, 325 Dodge, Desoto*. *1957 Desoto used 325 Dodge Poly for non-Hemi applications.

The same generally applies to Chrysler Hemis and Polys. To the best of my knowledge, there are no Desoto polys before the Dodge sourced ‘57 model, but there are high deck/low Desotos in the Hemi versions.

Ray

 

my father shoe horned a Poly from a Plymouth with with the dual quads into his 53 coronet after his Red Ram died ...
said it could keep up with his brothers 57 283 vette

 

My father runs a 326 poly in his 1959 Coronet.


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I flogged a 56 custom royal 2 door hard top 270 poly for several years. That was the last year for the good bodies. In 57 they came off the showroom floor with rust What engine is in the 56?
The number is on the top of the block just in front of the valley cover.
D631xxxx 270 2 bbl.
D632xxxx 315 2 bbl.
D633xxxx 315 4 bbl.
Good 315 crankshafts are getting to be like hens teeth. 270 has better availability.
The old Mopars didn't want to start if there was a thunderstorm in an adjacent state. The cure was to drill a couple of 3/16 or so holes in the distributor base for ventilation.
Slow starters were cured by installing a 6v unit from a 53-54-55. Have yours rewired.
The cast iron automatic is difficult to rebuild (and why would you?) An adapter with a 76 or later A727.
For some reason I like the 270dodge!

 

^^^ Or, a 1962 to '64 aluminum 727 from a 318 complete with pushbutton shifting. But the ball & trunnion put some people off. Or, one from a '65. The '65 was the same as the push button, but used a more conventional shifter. Why? Because it had a slip yoke. Several years ago Pork & Beaner mentioned in another thread that a '68 on up pump and input shaft could be used as this would allow an aftermarket converter to be run on the earlier transmission. I'm sure there is more to that conversion, but it makes one think don't it.
-Dave

 

Chryslerfan55,

Man,,that is a beautiful old Coronet,,,,,really nice lines ,,,,also,,,,classic style color scheme .
I hope your dad enjoys it,,,and drives t every chance he gets,,,very sharp looking!

Tommy

 

He does enjoy it, drives the wheels off the thing. Traded a ‘54 Merc for it(long story) used to belong to a little old lady (No, not THAT little old lady)


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There's the early hemi based Poly & the later "A" Polys. The hemi based Polys can be converted to Hemi, the A Poly can't different engine. Early Dodge, Plym & DeSoto Polys were Dodge hemi blocks. The '55 Chr 301 Poly is hemi based, the '57 Plym 301 is an A. There are differences between the A & LA engines.

 

As are the ‘56 331 and ‘57 354 Chrysler Polys..........

 

Excuse my absent mindedness but I failed to mention that my fathers Coronet is a 100 percent original ( numbers matching that is).


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I've had a 313 Oz Poly & cast iron push button T/f in my 1940 Dodge since 1973, shortened the cable to fit the late 60's Valiant shifter.........the poly runs a mild cam, Weiand 7503 intake, 600 Holley, Mallory twin point, Edlbrock finned covers bored to 325 & balanced.........goes o/k for this old fart..........Andyd

 

Would like to see more pictures of your Dodge Andy!

- EM

 

Great looking car!

- EM